Tropical Cyclone Dynamics Shaped by Aerosol-Cloud-Interactions: A Composite Perspective Using ICON Ensemble Simulations.

Tropical cyclones (TCs) pose a significant threat to coastal populations and ecosystems. To effectively mitigate TC risk, it is essential to understand their evolution under current and future climate conditions. One aspect of their development that remains unclear is the role of aerosol-cloud interactions (ACI). Satellite observations indicate that aerosols can invigorate convection in tropical deep convective clouds (Jiang et al., 2018). However, observations of ACI in TCs remain limited. In contrast, numerical simulations indicate that aerosol-induced convective invigoration can either weaken or strengthen TCs, depending on where the aerosols enter the storm (Lin et al., 2023; Hoarau et al., 2018).

In the future, aerosol concentrations are expected to decrease due to reductions in anthropogenic emissions (Riahi et al., 2017). The impact of this overall aerosol decline on TCs remains unclear. As part of the EU-funded CleanCloud project, our goal is to investigate TC dynamics in cleaner aerosol conditions to refine our understanding of ACI in TCs and improve future TC risk assessments.

We use the numerical weather prediction and climate model ICON (Zängl et al., 2015) in limited area mode using a 10 km horizontal resolution to run ensemble simulations of the North Atlantic TC season in 2020. Cloud processes are parameterized with a two-moment microphysics scheme (Seifert and Beheng, 2006) while deep convection parametrisation is disabled. Aerosols are uniformly prescribed in varying concentrations, allowing TCs to evolve in both clean and polluted conditions. By implementing a novel cyclone composite method that normalizes the storms by their eyewall location and extent, we evaluate the clean and polluted cyclone populations in terms of their circulation and structure. Our study compares TC activity on the storm scale in the 2020 TC season under both clean and polluted aerosol conditions, offering insights into how TC dynamics might be shaped by ACI.

 

Literature

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